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Information - Help 
ID = 2920
Great Britain (UK)
Developer: Common type Great Britain tube/semicond. 
Tube type:  Triode, vacuum   Power/Output 
  Ca. 1925 up to 1945 rare.
Identical to P425 = B405
Similar Tubes
Normally replaceable-slightly different:
Other base:
First year Sep.1928 - - Manufacturers Literature Leaflet
First Source (s)
Sep.1928 : - - Manufacturers Literature Marconi leaflet

Base Europe 4-Pin B4 (Eu A, E, 4A) 1914 (Codex=Foo)
Was used by Radio/TV-reception etc.
Filament Vf 4 Volts / If 0.25 Ampere / Direct / Battery =

Dull emitter super-power audio amplifier. 17mA anode current at 150V with 16.5 negative grid bias. 2.5Kohm impedance. Also made with UV base.

Dimensions (WHD)
incl. pins / tip
44 x 106 x mm / 1.73 x 4.17 x inch
Weight 46 g / 1.62 oz
Information source - - Manufacturers Literature   
Taschenbuch zum Röhren-Codex 1948/49   
History of the British Radio Valve to 1940
P425: National Valve Museum UK
Fin Stewart

P425: rtt
Michael Schlör

Jose Casas-Avalos

from Just Qvigstad

Usage in Models 1= 1930 ; 2= 1931 ; 1= 1932 ; 1= 1934 ; 1= 1937

Quantity of Models at with this tube (valve, valves, valvola, valvole, válvula, lampe):6

Forum contributions about this tube
Threads: 1 | Posts: 3
Hits: 2463     Replies: 2
P425 (P425)
Wolfgang Thiel
  1 Hi all

I would like to add a photo of a P425 from Osram. I can see there are various Models (Madzda, Lissen) and I'm not sure if the photo goes under the common tube type or a new Model? Can someone help me out.


Roy Johnson

Hi Wolfgang,

Please load to the P425_Mazda_Marconi.   These are closely the same and differ in detail from the other tubes of the same name.

Many thanks and best regards,


Ernst Erb

If a tube has the same designation and the same values - but quite different looks (bulb, base material etc.) then a member can create a variant, giving a short differency as name and filling in some text into the notes. The most important is - after acceptance of the variant to load up the pictures for the variant.

I believe that the P425 is not a common Europe but a common UK valve. Either Roy Johnson or Peter den Boer might know and change if that is right. What I don't know is if we can say it is UK and Commonwealth if common Britain - or if we should differenciate ... and have two different common for that.

End of forum contributions about this tube

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